Language:
كتاب السهو
22  
Forgetfulness in Prayer
(1)
Chapter: What is said regarding the Sahw: If someone gets up (for the third rak'a without sitting) after the second rak'a of a compulsory salat (prayer)
(1)
باب مَا جَاءَ فِي السَّهْوِ إِذَا قَامَ مِنْ رَكْعَتَىِ الْفَرِيضَةِ
Sahih al-Bukhari 1225

Narrated `Abdullah bin Buhaina:

Allah's Messenger (ﷺ) got up after the second rak`a of the Zuhr prayer without sitting in between (the second and the third rak`at). When he finished the prayer he performed two prostrations (of Sahu) and then finished the prayer with Taslim.

حَدَّثَنَا عَبْدُ اللَّهِ بْنُ يُوسُفَ، أَخْبَرَنَا مَالِكٌ، عَنْ يَحْيَى بْنِ سَعِيدٍ، عَنْ عَبْدِ الرَّحْمَنِ الأَعْرَجِ، عَنْ عَبْدِ اللَّهِ ابْنِ بُحَيْنَةَ ـ رضى الله عنه ـ أَنَّهُ قَالَ إِنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَامَ مِنِ اثْنَتَيْنِ مِنَ الظُّهْرِ لَمْ يَجْلِسْ بَيْنَهُمَا، فَلَمَّا قَضَى صَلاَتَهُ سَجَدَ سَجْدَتَيْنِ ثُمَّ سَلَّمَ بَعْدَ ذَلِكَ‏.‏
Reference : Sahih al-Bukhari 1225
In-book reference : Book 22, Hadith 2
USC-MSA web (English) reference : Vol. 2, Book 22, Hadith 316
  (deprecated numbering scheme)